The present invention generally relates to devices for removing undesirable deposits from the lumen of a blood vessel or from a stent positioned within a blood vessel, and more particularly, to atherectomy devices.
Vascular diseases, such as atherosclerosis and the like, have become quite prevalent in the modern day. These diseases may present themselves in a number of forms. Each form of vascular disease may require a different method of treatment to reduce or cure the harmful effects of the disease. Vascular diseases, for example, may take the form of deposits or growths in a patient""s vasculature which may restrict, in the case of a partial occlusion, or stop, in the case of a total occlusion, blood flow to a certain portion of the patient""s body. This can be particularly serious if, for example, such an occlusion occurs in a portion of the vasculature that supplies vital organs with blood or other necessary fluids.
To treat these diseases, a number of different therapies are being developed. While a number of invasive therapies are available, it is desirable to develop noninvasive therapies as well. Non-invasive therapies may be less risky than invasive ones, and may be more welcomed by the patient because of the possibility of decreased chances of infection, reduced post-operative pain, and less post-operative rehabilitation. One type of non-invasive therapy for vascular diseases is pharmaceutical in nature. Clot-busting drugs have been employed to help break up blood clots, which may be blocking a particular vascular lumen. Other drug therapies are also available. Further non-invasive, intravascular treatments exist that are not only pharmaceutical, but also revascularize blood vessels or lumens by mechanical means. Two examples of such intravascular therapies are balloon angioplasty and atherectomy that physically revascularize a portion of a patient""s vasculature.
Balloon angioplasty comprises a procedure wherein a balloon catheter is inserted intravascularly into a patient through a relatively small puncture, which may be located proximate the groin, and intravascularly navigated by a treating physician to the occluded vascular site. The balloon catheter includes a balloon or dilating member that is placed adjacent the vascular occlusion and then is inflated. Intravascular inflation of the dilating member by sufficient pressures, on the order of 5 to 12 atmospheres or so, causes the balloon to displace the occluding matter to revascularize the occluded lumen and thereby restore substantially normal blood flow through the revascularized portion of the vasculature. It is to be noted, however, that this procedure does not remove the occluding matter from the patient""s vasculature, but displaces and reforms it.
While balloon angioplasty is quite successful in substantially revascularizing many vascular lumens by reforming the occluding material, other occlusions may be difficult to treat with angioplasty. Specifically, some intravascular occlusions may be composed of an irregular, loose or heavily calcified material which may extend relatively far along a vessel or may extend adjacent a side branching vessel, and thus are not prone or susceptible to angioplastic treatment. Even if angioplasty is successful, thereby revascularizing the vessel and substantially restoring normal blood flow therethrough, there is a chance that the occlusion may recur. Recurrence of an occlusion may require repeated or alternative treatments given at the same intravascular site.
A relatively new technique to reduce the recurrence of occlusion after a balloon angioplasty procedure involves providing a stent at the revascularized site. A stent is a hollow tube, typically braided, that can be inserted into the vasculature of a patient in a compressed form. Once properly positioned at a desired site, the stent is expanded to hold the vessel open in an attempt to prevent restenosis. While this technique can help maintain blood flow past the site, it has been found that the occluding material often migrates through the interstices of the stent braid, and may again occlude the vessel. This phenomenon is sometimes referred to as interstitial hyperplasia.
Accordingly, attempts have been made to develop other alternative mechanical methods of non-invasive, intravascular treatment in an effort to provide another way of revascularizing an occluded vessel and of restoring blood flow through the relevant vasculature. These alternative treatments may have particular utility with certain vascular occlusions, or may provide added benefits to a patient when combined with balloon angioplasty and/or drug therapies.
One such alternative mechanical treatment method involves removal, not displacement, as is the case with balloon angioplasty, of the material occluding a vascular lumen. Such treatment devices, sometimes referred to as atherectomy devices, use a variety of means, such as rotating cutters or ablaters, for example, to remove the occluding material. The rotating cutters may be particularly useful in removing certain vascular occlusions.
In operation, an atherectomy device is typically advanced over a guide wire placed in vivo until the device is positioned just proximal to the occluded site. A motor is used to rotate a driveshaft coupled to the device, and the device is moved through the occluded vessel. Frequently, an aspiration device is utilized in conjunction with the device to remove the loose particulate broken off by the device so that the particulate is not introduced into the body. Typically, a conventional aspiration device consists of a catheter in fluid communication with a vacuum source or negative pressure such as a vacuum pump or bottle. The catheter, generally surrounding the driveshaft, is advanced to the occlusion site over the guide wire to remove the loose particulate.
However, problems can occur when treating various vessels of the patient. For example, in saphenous vein grafts (SVG) and with stented vessels, the occluding material or gromous has a tendency to be more loosely organized and brittle, which makes the material friable. Therefore, in operation, conventional devices tend to break off large pieces of this material rather easily due to its morphology, instead of ablating it. These large particulate are then sucked into the mouth of the aspirating catheter, causing the loose particulate to become lodged in the mouth of the catheter. As a result, the occlusion site is presented with a lack of vacuum pressure that could hinder the aspiration process.
Therefore, there exists a need for an improved ablation burr system and process for removal of large, liberated particulate within an occluded blood vessel to overcome the deficiencies in the prior art.
An ablation system is provided to overcome the deficiencies in the prior art. The ablation system comprises an atherectomy device and an aspiration catheter, each routed to a position just proximal to a lesion within a patient""s vessel to ablate and remove the lesion so that blood flow through the vessel is adequately restored.
In one embodiment of the invention, an ablation system includes a driveshaft, an ablation burr coupled to the driveshaft and an aspiration catheter. The aspiration catheter has a trap for collecting particles of occluding matter that are ablated by the burr.
In accordance with another aspect of the present invention, a mechanism is provided that cooperates with the trap on the aspiration catheter to clear collected particles from the trap.
In accordance with yet another aspect of the present invention, a system for ablating an occlusion in a patient""s vessel comprises an ablation burr having a front surface and a rear surface, and being rotatable to ablate the occlusion. The system also comprises an aspiration catheter having proximal and distal ends. The catheter includes a lumen that extends longitudinally therethrough. The lumen forms an aspiration mouth at the distal end of the aspiration catheter, where the aspiration catheter includes a tapered inner surface defining a portion of the lumen.
In accordance with still another aspect of the present invention, a method is provided for ablating a lesion in a patient""s vessel using an ablation burr system. An atherectomy burr is routed to a position just proximal to the lesion, the burr having a downwardly tapering rear surface. An aspiration catheter is routed to a position just proximal to the burr, the aspiration catheter having proximal and distal ends and including a lumen that extends longitudinally therethrough. The lumen forms an aspiration mouth at the distal end of the aspiration catheter, where the aspiration catheter includes a tapered inner surface defining a portion of the lumen. The burr is advanced distally through the lesion causing loose particulate to separate from the vessel wall. The loose particulate is aspirated with the aspiration catheter. The aspiration mouth of the aspiration catheter is cleared by pulling the burr proximally toward the aspiration catheter so that the burr can break down the loose particulate for removal by the catheter.